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Ecology and behaviour of frogs, with emphasis on the Green and Golden Bell Frog, Southern Bell Frog and Striped Marsh Frog
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Current knowledge
General frog biology
Our knowledge of the general biology of frogs in New South Wales and elsewhere in Australia is poor. Descriptions of habitats are vague and imprecise at best and non-existent at worst. Information concerning the diet of adult frogs is almost non-existent. There is no published information regarding the natural diets of tadpoles.
Frog population biology
Our knowledge in relation to the various factors that determine population biology of Australian frogs is even worse. For almost all species, there is no available information about factors such as:
- rates of growth and development
- age at maturity
- survival
- longevity
- movements
- mate selection
- sources of mortality
Even such a basic component as average clutch size is unknown for most species.
Frog community biology
Our knowledge of frog community biology is similarly poor. We know that some sites have more co-occurring frog species than others, but we do not understand why this should be so. This means that we cannot accurately predict which species will be present at particular sites.
Even for the Green and Golden Bell Frog (GGBF), which is undoubtedly the most studied Australian frog, our knowledge is severely limited. While we know, for example, that they are capable of moving distances of 10 km or more, we have little idea concerning typical patterns of movement. We know that they can live over ten years in captivity but have no information concerning typical rates of survival or longevity. We do not know what factors determine distribution or abundance, nor how such factors might operate.
Strategies for frog conservation
Our strategies for conserving frogs and stopping their declines are currently restricted to simple protection of habitat. If we know that a particular frog species occurs in an area and we know what habitats it uses within this area, then we may simplistically attempt to conserve the species in the area by avoiding or preventing disturbance of these habitats through human activities. We may similarly hope to achieve recovery of a threatened species simply by stopping human disturbance of habitats used by the species.
Even for the well-studied GGBF, conservation and recovery are problematic. We know that the species can thrive in some completely artificial sites and we should be able to develop and enhance habitat for the species, if we could create the right conditions. We have also been able to evaluate some aspects of habitat that affect the frog. Nonetheless, however, our ability to design new habitat for the species cannot be considered good, as we have not so far succeeded in introducing the species into any new sites.
Achieving frog population management goals
To effectively manage populations and habitats of frogs and to stop and reverse frog declines, it is necessary to understand what factors determine the distribution and abundance of each frog species, and how these factors operate. However, we do not currently possess this fundamental understanding for any Australian frog species.
The project: frog species profiles
Green and Golden Bell Frog
The Green and Golden Bell Frog (GGBF) (Litoria aurea) has disappeared from much of its original distribution in New South Wales and is presently restricted to about 20 known locations in New South Wales. Its decline is continuing, but new sites are still being discovered. During the last few years, new populations have, for example, been discovered at Hat Head National Park and Medowie, and very recent reports suggest that it may still be present at North Wyong where it has not been recorded for over 10 years.
Southern Bell Frog
The Southern Bell Frog (Litoria raniformis) has similarly declined, and both of these Bell frog species are considered endangered in New South Wales. The SBF has colonised some areas of irrigation-based agriculture and is, in fact, quite common and widespread in one such area where rice is the major crop. In other irrigation areas, however, this species has disappeared or is less abundant. It has disappeared from almost all areas of natural habitat within New South Wales.
Striped Marsh Frog
The Striped Marsh Frog (Limnodynastes peronii) is perhaps the most abundant and widespread frog species in south-eastern Australia, yet surprisingly few studies have focused on it. It is, in many ways, biologically similar to the GGBF, yet it is very common while the GGBF is rare and endangered. We became interested in this species because it is present and often abundant at almost all sites where the GGBF is found.
The project: goals
The broad goals of this project are to:
- increase, through field investigations, our knowledge and understanding of the biology of frogs of New South Wales, with an emphasis on the Green and Golden Bell Frog, Southern Bell Frog and Striped Marsh Frog
- make this knowledge and understanding available to relevant stakeholders
- encourage the use of this knowledge/ understanding in environmental management
- participate in programs that aim to protect/ conserve frogs and/ or their environments
The project: study sites
Study sites have been chosen so that they include a range in population sizes for the species, encompass a range of habitat conditions and experience a range in levels of human disturbance. Our principal study sites are:
- Broughton Island
- North Avoca
- Long Reef
Within each site various survey locations and survey routes are chosen.
- Survey locations are physically distinct areas where tadpoles and/or frogs are found. They are mostly water bodies but may also include terrestrial areas such as urban backyards at North Avoca.
- Survey routes are pathways around, through and between the survey locations, and surveys for frogs and tadpoles are carried out along them. Survey routes are chosen so that the people available can survey them in two to three hours for frogs or tadpoles.
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